1. Field of the Invention
The present invention relates to master control mechanisms for mechanical remote control of manually shifted change gear transmissions. In particular, the present invention relates to remote master shift control mechanisms for shifting a manual change gear transmission which control mechanism is adapted for substantially universal use in vehicles of various configurations.
2. Description of the Prior Art
Remote master shift control mechanisms for shifting manual change gear transmissions are well known in the prior art and examples thereof may be seen by reference to U.S. Pat. Nos. 2,040,594; 4,104,929; 4,269,282; 4,275,612; 4,311,064, and 4,348,915, the disclosures of which are all hereby incorporated by reference.
Typically, such remote master shift control mechanisms are utilized in cab-over-engine type trucks or the like wherein the vehicle operators cab is located remotely from the transmission shift bar housing assembly.
The remotely controlled manually shifted change gear transmissions typically include a shift bar housing assembly comprising a plurality of axially slideable shift rails, each of which carry a shift fork or yoke thereon. A transversely mounted shift shaft is rotatably and axially moveably mounted in the shift bar housing assembly and carries a shift finger fixed thereto. The shift shaft is selectively axially moved in a direction transverse to the axes of the shift rails to align the shift finger with the shift block assembly or notch on a selected shift rail and then the shift shaft is selectively rotated to cause the shift finger to engage the selected shift block assembly to impart a desired axial movement to the selected shift rail and shift fork carried thereby. Remotely controlled transmissions utilizing a remotely controlled slave shift lever pivotably mounted at the transmission are also known in the prior art. Shift bar housing assemblies of various types for remotely controlled transmissions may be seen by reference to U.S Patent Nos. 2,040,595; 3,857,299; 4,104,929; 4,266,438; 4,269,282 and 4,275,612 all of which are hereby incorporated by reference.
Selected rotational and axial movement of the shift shaft, or pivotal movement of a slaved shift lever, is accomplished by means of a control or reach rod, also called a connecting rod, which extends generally transverse to the shift shaft and which may be selectively axially moved and/or rotated about its axis. Typically, a torque arm assembly, crank assembly or similar linkage is pivotably mounted to an end of the control rod, mounted to a reaction member associated with the shift bar housing and fixedly mounted to an end of the shift shaft whereby rotational movement of the control rod will impart an axial movement to the shift shaft and an axial movement of the control rod will impart a rotational movement to the shift shaft. The remote master shift control is typically located in the vehicle operators cab, forward of the transmission, for manual manipulation by the vehicle operator to impart a selected rotational and/or axial movement to the reach rod.
Synchronized mechanical transmissions are also well known in the prior art and may be seen by reference to U.S. Patent Nos. 4,307,624; 3,929,029 and 3,221,851, all of which are hereby incorporated by reference. Typically, such transmissions comprise constantly meshed gears on parallel shafts with synchronized positive clutches to selectively clutch a selected one of the gears for rotation with one of the shafts. Such synchronized positive clutch assemblies usually comprise an axially fixed positive clutch member (usually fixed to a gear) and an axially slideable clutch member (usually splined to a shaft for rotation therewith and axial movement relative thereto) movable toward and away from the fixed positive clutch member. The axially slideable positive clutch member is typically selectively axially moved by one of the shift forks carried by a shift rail. The synchronized clutch assembly includes a pair of friction surfaces defining a friction synchronizer clutch for causing the two positive clutch members to rotate at a synchronous or substantially synchronous speed, which friction surfaces require a relatively large axial force for proper operation in heavy duty transmissions such as are used in heavy duty trucks and the like. Accordingly, in synchronized mechanical transmissions, especially synchronized mechanical transmissions for relatively heavy duty use, the force required to rotate the shift shaft to axially move a selected shift rail is often considerably greater than the force required to axially move the shift shaft to select a desired shift rail.
The prior art remote master shift control mechanisms for mechanically shifting remote manual change gear transmissions, especially heavy duty synchronized transmissions, were not totally satisfactory as the remote master shift control mechanisms were not well suitable for substantially universal use with a large variety of vehicle configurations, were not suited for use in both vehicle configurations requiring the use of a crank mechanism at the master control unit and vehicle configurations allowing the elimination of the crank mechanism at the master control unit, required attachment to the reach or connecting rod in a manner wherein the lever member axially moving and/or rotating the crank mechanism was not perpendicular to the axis of the reach rod which results in undesirable movement of the master shift lever along an oblique path, were not easily adapated to allow variation of the plane of the shift pattern in the operators cab to best utilize the cab configuration and/or maximize convenience to the operator while maintaining the crank operating lever substantially perpendicular to the axis of the reach rod and/or did not provide means at the master control assembly for providing independent mechanical advantage in the rear selection and rear engagement modes of operation.